civilian 30.5 motor # should start with E
EDA would be a 1941 frame number: 541101 - up
E is the engine, D is the decade, A is the year in the decade.
military 30.5 motor: GDA, serial: 741101 - up
45 motor: FDO for 1940, FDA - 1941
serial #: 640101 - up , 641101 - up
VIN # is on left rear lower shock mount (at least that's where it is on the 74's)
I don't see how what any year someone registers a bike would change the factory stamping on the frame, HMMM? And if it was an option then the first three number/letter combo should agree and the last part of the serial numbers should match. If they don't then it must have been a nonfactory option ( could of been an option 20 - 30 years after it was built). Get my drift? Lotta flakey people out there inventin' stuff.